Mesh network technology can be used to provide a novel metropolitan communication network implementation that may achieve high bandwidth, high survivability through autonomous and self-healing operation, high availability through angle and geographic diversity, and the ability to “harden” network elements using “N+1” networking rather than the traditional “N+N” networking. High speed wireless technology allows the benefits of the mesh to be exploited while also benefiting from the cost-effectiveness and rapid deployment attributes of wireless communications.
Wireless mesh networks have two forms, including unconstrained meshes and constrained meshes. Unconstrained meshes often employ broad-beam or omni-directional antennas, which allow a given mesh node to “see” many other mesh nodes. Communication paths, which may be either primary paths or backup/re-route paths, are established with other nodes in an unconstrained manner. In this case, network routing is somewhat autonomous and as such, performance attributes such as delay, delay variability, failure re-route dead time, etc. can be somewhat unpredictable.
Constrained meshes use a restricted set of paths for primary connectivity and re-routing. A network operator or other personnel, or in some cases a control system or software, determines best paths in the mesh and enforces these paths. Delay, delay variability, failure re-route dead time, and possibly other performance attributes are therefore made more predictable.
Within the category of constrained meshes, a static array of wide-beam or sectorized antennas is typically used to form usable mesh network links between nodes. These systems sometimes use switch matrices to select antennas from the static array in order to connect radio electronics to specific antenna sectors of interest. Due to the wide-beam nature of the antennas, however, these systems do not provide high system gain or spatial rejection of interference.
An alternate approach is to use narrow-beam antennas that are oriented or aligned to form narrow beams between nodes within a mesh sub-circuit. The narrow beams allow the system to achieve such advantages as mesh network construction using point-to-point or area radio service licenses, very high capacities, individual scaling of mesh links independently of one another, very high system gain and therefore increased wireless range and high link availability, and a high degree of interference rejection.
Wireless mesh network equipment such as network nodes tends to be relatively bulky and unsightly, which can present challenges in environments where physical space is limited, or in residential locations or other deployments where aesthetics are important. Narrow-beam directional antennas offer some advantages over omni-directional or wide-beam antenna implementations as noted above, but may require a higher number of antenna elements and accordingly more physical space to provide a desired level of wireless coverage.
For example, various wireless access technologies employ sectorized antenna arrays in order to deliver service to a roughly circular coverage area where access customers or sites may exist. These antenna arrays are typically 4- or 6-sectored designs in order to fit within a larger metropolitan area coverage scheme. Some examples of these systems are cellular, Personal Communication System (PCS), and Global System for Mobile communications (GSM) mobile telephone systems, IEEE 802.11 (“WiFi”) systems, IEEE 802.16 (“WIMAX”) systems, and systems based on Local Multipoint Distribution Service (LMDS) or Local Multipoint Communications System (LMCS). As will be apparent to those skilled in the art of communications, IEEE 802.11 and IEEE 802.16 refer to sets of specifications that are available from the Institute of Electrical and Electronics Engineers (IEEE).
In many instances, the data and/or voice traffic in these systems is aggregated at base or hub station locations. At these locations, it is common for the traffic to be connected to one or more wireless backhaul radios for subsequent backhaul into a core network. The wireless backhaul function may be implemented using various transport technologies, such as point-to-point links for carrying Time Division Multiplexing (TDM), Synchronous Optical Network (SONET), or Ethernet traffic for instance, SONET rings, or Ethernet rings or meshes.
Wireless backhaul is traditionally implemented using backhaul radio systems that are separate network elements from access system elements and employ separate antenna systems. Backhaul radio system antennas are typically larger than access system antennas and have more highly focused beams.
In addition, an access system may be multi-functional, supporting both end user network access using area-coverage antenna systems and numerous dedicated point-to-point links for communications with other, possibly fixed, access sites such as enterprise buildings, cellular tower/building sites, etc. As with the wireless backhaul systems described above, these dedicated links may also use individual focused beams to support high bandwidth, high performance wireless communication links.
Therefore, at a given hub location, there may be numerous antennas supporting the access area coverage function and numerous other antennas supporting any of various other functions, such as point-to-point beams for wireless backhaul or links to other access sites.
In order to control the antenna counts and thus physical space requirements, various access technologies have been integrated into single sector antennas that have multiple functions. Some examples of these are dual mode cellular-PCS antennas, which include both 800-900 MHz and 1800-1900 MHz sector arrays. Another approach for conserving space, and to some degree cost, is to share other resources than antennas, such as sharing radio electronics between multiple antenna elements or wireless links. When antenna and/or radio resources are shared in this manner, however, the shared resources tend to become scarce, resulting in diminished capacity, lower survivability, and decreased availability.
Thus, there remains a need for improved network communication apparatus, techniques, and antenna structures.